The present invention relates to a method of contraception and compositions useful therefor that are applicable to males and females wherein the generation, maturation, motility and viability of sperm is affected by direct application of minerals in bioavailable form to the sperm or developing sperm in the target organ. Direct application of minerals in bioavailable form avoids the side effects found with other methods which rely on hormones or from the passage of a drug through the digestive tract.
Various water soluble minerals are toxic to sperm and have been injected into the testis or epididymis and been found effective at inhibiting the generation or maturation of sperm in the seminiferous or epididymal epithelium. They have also been found effective in vitro at inhibiting sperm motility and viability and postulated as a vaginal, cervical, uterine or tubal contraceptive in females. These methods, however, have not been put into commercial use because of certain adverse side effects.
To avoid adverse side effects in vivo, lower levels of less toxic materials are clearly preferred. To be effective and avoid hurting the subject, however, such materials must be in a form which is physiologically acceptable and cell permeable. Most water soluble minerals such as zinc chloride, zinc sulfate, zinc tannate and the like have proved too acidic to be commercially acceptable and cannot be neutralized with sodium hydroxide or sodium bicarbonate without effecting the stability of the solution or introducing an unacceptable level of sodium or other counterion.
In view of the above, it is an object of the present invention to provide a class of cell permeable physiologically acceptable water soluble minerals which are effective at inhibiting generation, maturation, motility and viability of sperm when applied in the testis, epididymis or vas deferens or in the vagina, cervix, uterus or fallopian tubes and which are not too acidic, caustic or astringent to cause discomfort to the subject. Other objects and features will be in part apparent and in part pointed out hereinafter. The invention accordingly comprises the methods and compositions hereinafter described and equivalents thereof, the scope of the invention being indicated by the subjoined claims.